Many free-flowing granular commodities are commonly transported in railcars called “bottom discharge covered hopper cars”. These cars have a tank-like upper body on a lower body consisting of several tapered hopper sections, commonly three or four in number, terminating in rectangular discharge openings closed and sealed by horizontally sliding gate plates housed in frames. These assemblies are called gravity discharge gates. The cars are loaded though either circular or more commonly trough-like longitudinal hatch openings in the roof, such trough hatch openings being covered and sealed by hinged hatch covers.
A number of the normally free-flowing granular commodities transported in hopper cars have a tendency under certain conditions to bond, or “cake”, during transit into a more viscous mass that retards their normal free-flowing characteristics. In some cases, this caked mass can have a very significant degree of structural integrity such that it will not flow at all under gravity alone but must first be broken up, or “crumbled” through applied mechanical means.
One commodity that has this tendency to cake is distiller's dried grain, known as “DDG” in the industry. The most voluminous example of DDG in North America is the residue from the process of making ethanol from corn. This residue product is excellent feed for livestock and is transported in bulk from the ethanol plants, located principally in central North America, to all regions in North America, employing approximately 11,000 very large bottom discharge covered hopper cars assigned specifically to this service. Thus, the effectiveness of this transport means is commercially important and the tendency to cake is a serious impediment in this respect.
There are a variety of means employed to crumble caked material such as DDG to permit it to flow out through the discharge gates. The most common method is to vibrate the hopper car slope sheets in order to loosen the bulk material and keep it somewhat fluidized as it flows. This is accomplished through the application of special vibrators into mounting brackets welded to the slope sheets of the tapered hopper sections of the hopper cars. All unloading facilities that handle DDG and like commodities are equipped with such vibrators, most driven by compressed air.
Very difficult DDG loads with exceedingly tenacious caking are fairly common, particularly in the summer months. In such cases, the side-mounted vibrators are not sufficient to disturb and break up the caked DDG inside, and additional means must be employed. One such means is through manual “picking” with a crow-bar applied up into the caked load through the bottom discharge gate opening in an attempt to cause the caked load to flow. The reach up from the bottom is limited and in many cases insufficient to cause free flow in the caked load.
The caked DDG can be sufficiently sticky that it will adhere to the sides of the hopper car and actually support overhanging structures in the load where the adjacent DDG has broken up and flowed away through the open discharge gates below. In these more difficult situations additional mechanical means are employed beyond the normal external vibration and picking through the outlet gate described above. Such means include more violent vibration waves caused by physical hammering of the sides of the hopper car with sledges as well as the use of large, pointed, poker-like prodding tools mounted on special hydraulic/mechanical machinery located on platforms above the hopper cars. These large prods are inserted through the loading hatches and manipulated to pick at the caked DDG from above. These large devices are effective at causing the caked loads to flow, but they are very expensive to buy and operate and only the larger unloading facilities can afford them.
It will be readily appreciated that this physical hammering with sledges and blind prodding from above with large, clumsy hydraulic equipment is inevitably extremely damaging, leaving large dents at each contact with the rail car hopper sheets. It will be further appreciated that an alternate, non-damaging and cost effective means of crumbling caked material would be of significant benefit to the industry. The purpose of the present invention is to provide such a cost effective mechanical cake-crumbling means, installed within the railcar hoppers themselves.
There are other means that have been tried, including chemical additives to the DDG itself and other internally mounted load disturbing means but all have proven to be either too expensive or ineffective for breaking DDG when under the most severe caking conditions.